1. Field of the Invention
The present invention relates to a photoelectric sensor for detecting the presence/absence of an object using a light-emitting device and a light-receiving device.
2. Description of the Related Art
This kind of photoelectric sensor has a basic configuration of detecting the presence/absence of an object in a detection area where a light-emitting area of a light-emitting device and a light-receiving area of a light-receiving device are overlapped with each other. More specifically, when an object passes through the detection area, light emitted from the light-emitting device is reflected from the object, and is received by the light-receiving device. As a result, a level of a signal output from the light-receiving device is changed, so that the intrusion of the object is detected.
The detection area is determined by the positional relationship between the light-emitting device and the light-receiving device, the orientation of the light-emitting device and the light-receiving device, and the like. When a plurality of light-emitting devices and light-receiving devices is used, the presence/absence of an object can be detected over a plurality of detection areas (see Japanese Patent Laid-Open Publication No. 2002-168967, for example).
However, in the case where a plurality of light-emitting devices and light-receiving devices is used, there is a problem in that it is very difficult to realize miniaturization and cost-reduction of an apparatus.